Research in our laboratory during the coming year will continue to focus on the relationship between the sympathetic nervous system and renin secretion. Whereas in the past such studies have been carried out in the whole animal (anesthetized dogs), during the coming year we intend to develop an in vitro model, since side effects of the drugs used in our whole animal studies (i.e., blood pressure changes, alterations in plasma and probably intracellular potassium) have made interpretation of our data difficult. Our model, at least initially, will be a suspension of isolated intact rat glomeruli. Initial attempts with this model have shown that glomeuli obtained in this manner do secrete measurable amounts of renin into the media. The next step will be to determine whether sympathomimetic agonists and antagonists alter this renin secretion in the same directions as observed in the whole animal. In addition, we will attempt to grow glomeruli in culture with two purposes in mind. It may be possible to clone from such a preparation juxtaglomerular cells themselves, particularly if our starting material is a renin secreting tumor. Such a preparation may be an even better model for studying renin secretion but, in addition, may provide a means of looking at control of renin synthesis, a very much neglected area of renin research.